Structure and antigenic behaviour of kappa I-immunoglobulin light-chain amyloid proteins.

N-terminal amino acid sequence analysis of three amyloid fibril subunit proteins from three different patients revealed a primary structure homologous to KI immunoglobulin light chains. In double immunodiffusion an antiserum against one of these amyloid proteins reacted with all three amyloids showing one line of identity, while an antiserum against one of the other amyloid proteins reacted with only one of the nonhomologous amyloids, appearing as partial identity, These two antisera did not react with any amyloid of lambda I, lambda IV or lambda VI type. The results confirm previous experiments, in which it has been shown that some antisera against amyloid proteins of immunoglobulin origin give a reaction of identity with other amyloids in the same immunoglobulin subgroup, probably owing to subgroup specific antigenic determinants in the variable segments. It was found that the distribution of amyloid varied widely among the three patients. There does not seem to be any correlation between the type of manifestation of amyloidosis and the type of immunoglobulin light chain forming the amyloid fibril.